Rinse compositions



Patented June 17. 194 1 Franklin T. Peters,

E. I. du Pont de Wilmington, Del., assignor to Nemours & Company, Wilmington, DeL, a corporation of Delaware N Drawing. Application April 14, 1944.

Serial No. 531,121

1 Claim.

This invention relates to improved germicidal compositions and, more particularly, to germicidal rinse compositions. v

A variety of chlorine-containing compounds have been used in germicidal compositions for various purposes but they are not completely satisfactory in all respects. Some germicidal compositions consistingof chlorine disinfecting compounds in combination with wetting agents and alkaline buffers have satisfactory germicidal activity. However, these compositions in the solid state in which they are normally shipped or stored lose appreciable quantities of active chlorine over relatively short periods of time, particularly under conditions of high temperature and humidity. The requirements for satisfactory utility are, in fact, so severe that for germicidal rinse compositions some large users are forced to the use of relatively expensive materials such as N,N-dichloroazodicarbonamidine which is not readily available in suflicient amount. N,N-dichlorodimethylhydantoin has also'been proposed as a sterilizing agent in water, but it is not effective as a germicidal agent under alkaline conditions. Because of this it is not satisfactory for use in applications such as rinsing dishes which have been washed in solutions containing alkaline detergents as the detergent carried with wet dishes into the germicidal rinse-solution soon makes the rinse solution alkaline and consequently inefiective as a germicide for bacteria, such as Escherichia coli.

It is an object of this invention, therefora'to provide a germicidal composition which will have satisfactory stability for long periods of time when stored in the solid state under conditions of high temperature and humidity. A further object is to furnish a rinse composition which will continue to have a strong germicidal action even if alkaline detergents contaminate the rinse solution. A still further object is to provide such a composition which is relatively low in cost and readily available. Other objects will appear hereinafter.

These objects are accomplished by the following invention which comprises a composition for use in germicidal rinse compositions containing as essential ingredients an N-chlorohydantoin andan acidic bufier, i. e., an acid, including an acid reacting salt,

preferably3.5 to 4.5. v

The more detailed practice of the invention is illustrated by the following examples, wherein capable of maintaining the rinse solution at a pH of from 2.'0 't'o 6.5 and many forms of the invention other than these specific embodiments.

Example I A uniform mixture of 27.8 parts of 1,3-dichloro- 5,5-dimethylhydantoin, 55.5 parts of sodium dihydrogen phosphatemonohydrate and 16.7 parts of fatty alcohol sulufate surface active agent is prepared by mixing the ingredients together in the dry state in a suitable container. One part of this dry mixture is dissolved by stirring in 3,730 parts of water at room temperature for a few minutes. The resulting solution (prepared in a glass container) has a pHof 3.57 and a, surface tension of 36 dynes/cm., and contains 40 parts per million of active chlorine. This solution kills all the Escherichia coli in the standard test set forth below. This test was developed to determine the efliciency of germicidal rinse compositions in destroying bacteria in the presence of organic matter such as would be encountered in dish water or rinse water. This amount of active chlorine in the'solution is the minimal disinfecting dose as determined by the procedure described below.

To 0.95 cc. portions of 2% sterile peptone (such as Bacto-Peptone manufactured by the Difco Laboratories) solution in test tubes are added solutions of varying proportions of the chlorine disinfecting composition in 8.51 cc. of sterile distilled water, Different amounts of the chlorine containing composition are added to different 8.51 cc. portions of distilled water. After the addition of the peptone to the chlorine-containing solution, the mixture is well shaken, and it then has a volume of 9.46 cc. The chlorinated peptone water is held at 45 C. for one-half hour. After this time a quantity of diluted 18-hour broth culture of American type culture collection Strain No. 27 Escherichia coli is added to each tube so that the bacterial count of the chlorinated peptone water will be about 500 organisms per cc. at the time of the addition (0.2 cc of a /1000 dilution of 18-hour broth culture). The bacterial suspension in each tube of the chlorinated peptone water samples is well mixed and after five minutes dechlorinated by the addition of one drop of 10% sodium sulfite solution. Dupllcate'plates parts given are by weight; There are, of course,

are poured from each of the concentrations of chlorine germicidau'sing one cc.-of the dechlorinated sample.v ,The lowest concentration of chlorine germicide in peptone water, inoculated and treated as above, which after culture for 48 hours at 37 C. shows no colonies of Escherichia coli on either plate, constitutes the minimal disinfecting dose.

n 3 Example II Example III The following ingredients are mixed in the usual manner in the dry state until a uniform composition is obtained: 7.? parts of 1,3-dichloro- 5,5-dimethylhydantoin, '17 parts of sodium dihydrogen phosphate monohydrate and 15.3 parts of fatty alcohol sulfate. One part of this dry mixture is dissolved in 1,620 parts of water. The

resulting solution (made in a glass container) has a pH of 3.8, a surface tension of 36 dynes/cm., and contains 30 parts per million of active chlorine. This is the minimal disinfecting dose for this particular composition, as determined by the standard test.

Example IV The following ingredients are mixed together in the customary manner until uniform: 7.? parts of N monochloro C ,C dimethylhydantoin, 7'7

parts of succinic acid and 16.3 parts of'fatty alcohol sulfate. One part of this dry mixture is dissolved in 1,416 parts of water. The resulting solution has a pH (in glass) of 2.68, a surface tension of 42 dynes/cm. and contains 30 parts per million of active chlorine. This is the minimal disinfecting dose as determined by the test described previously.

Example V Five parts of 1,3-dichloro--5,5-dimethylhydantoin and 95 parts of sodium dihydrogen phosphate monohydrate are mixed together until a uniform mixture is obtained. The mixture is stored in closed brown glass bottles at room temperature. Samples are removed periodically and tested for retension of active chlorine by titration with standard sodium thiosulfate solution. After 12weeks at room temperature this composition retains 94% of its active chlorine.

Any N-chlorohydantoin may be used in the preparation of the compositions of this invention, although it is preferred to use N-chloro-C,C-dialkylhydantoins. In addition to the specific N- chloroh'ydantoins described in the examples there may be employed the following exemplary species: methylene bis(N-chloro C,C dimethylhydantoin) 1,3-dichloro-5-methyl 5 isobutylhydantoin, 1,3-dichloro-5-methyl 5 ethylhydantoin, 1,3 dichloro 5,5 diisobutylhydantoin, 1,3 dichloro 5 methyl 5 n amylhydantoin and N-monochloro-C,C-diethylhydantoin.

A wide variety of acidic buffers is suitable for use in the compositions in this invention. Organic acids or acid-reacting salts of organic or inorganic acids are equally suitable. The essential requirement to be met, in selecting the acid buffer is that it be capable of maintaining the germicidal rinse solution in which it is incorporated at a pH of less than 6.5. For optimum germicidal properties, it is preferred that the pH be maintained at between 3.5 and 4.5 (as determined in -rinse solution made up in glass containers). The critical nature of the pH of Efiect of pH on Germicidal activity of dichlorodimethylhydantoin Minimal Disinfecting Dose Parts/Million of Active Chlorine No kill at P. P. M.

In addition to the specific buffers described in the examples, others which may be used in the compositions of this invention with equal effectiveness include potassium dihydrogen phosphate, sodium hydrogen sulfate, potassium acid phthalate, potassium acid tartrate, maleic acid and fumaric acid. If desired, mixtures of one or more of these. or other, acidic buffers may be used. While compositions of lower pH have greater germicidal activity there is a practical limit beyond which it is not desirable to go sincesolutions of very,

low pH, e. g., below 2.0, arecuite corrosive to metal containers which may be used for handling the solutions. The preferred limits 'of pH mentioned are the values obtained'when the solution is made up and tested in glass apparatus.

While the presence of a surface active agent is not essential in compositions of this invention, in some cases it is advantageous to include one. For example, it is particularly desirable to include a surface active agent when the rinse solution is to be applied to surfaces which may be contaminated with a small amount of grease or oil. In such cases, the presence of a surface active agent which will lower the surface tension to 40 dynes/cm. or less is desirable in order to increase the rate of penetration of the active chlorine to all parts of the surface in order to kill all bacteria rapidly. Surface active agents of various types, such as anionic, nonionic, and

face active agent is sodium dodecylsulfate. Other anionic surface active agents which may be used with satisfactoryresults include alkali metal al-' kylarylsulfonates, sulfonated naphthalene-formaldehyde condensation products, sodium alkylnaphthalenesulfonates, sulfonated White oil, etc. The proportion of surface active agents used can be varied over rather wide limits; the only requirement being that enough surface active agent is used to reduce the surface tension of the final germicidal rinse solution to a value giving satisfactory penetration of grease films; a value of 40 dynes/ cm. or less is preferred for some uses. Concentrations of fatty alcohol sulfate ranging from about 2.65% to 39.9% of the total weight of the chlorohydantoin-acid buffer-surface active agent about 60 parts per million of active chlorine for the compositions of this invention. The proportion of acid buffer in relation to the active chlorine compound is that which. will supply sulficient acid or acid reacting salt to neutralize all the alkali expected to be introduced into the rinse solution, for example, during its use, so that it maintains the pH of the solution below 6.5 until all the active chlorine has been used up. Proportions of acid buffer ranging from 80% or less to 1000% or more of the weight of the chlorohydantoin have been found effective. In a preferred composition for use as'a germicidal rinse for dishes the amount of sodium dihydrogen phosphate is 1000% of the weight of the chlorohydantoin. The amount of wetting agent (or surface active agent) in the dry mixture may also be varied over wide limits. Dry mixtures containing from 30% to over 700% (based on the weight of chlorohydantoin) of surface active agent are satisfactory. In a preferred composition for use as a germicidal rinse for dishes an amount equal to about 200% of'the weight of chlorohydantoin is used.

The only limit to the amount of the dry mixture to be used in preparing the germicidal solution is that suiiicient dry mixture be used so that at least the minimal disinfecting dose of ,active chlorine is obtained in the final solution. As indicated above, this is about -60 parts per million of active chlorine. Larger proportions than this may be used if desired, but for economic reasons the minimum amount of active chlorine required to kill all the bacteria expected to be present is suflicient.

The N,N'-dichlorohydantoins are soluble in water but their rate of solution is rather slow for use in certain applications. For such applications, where a higher rate of solubility is desired, this can beaccomplished by incorporating about an equal weight of 5,5-dimethylhydantoin with the dichlorohydantoin. The incorporation of this dimethylhydantoin does not impair the germicidal activity of the dlchlorohydantoin. .If a

greater rate of solubility of the chlorohydantoins is desired, the commercially available solid is subiected to a comminuting treatment to reduce its particle size. Treatment with a micronizer or a micro pulverizer increases the rate of solubility of dicholorodimethylhydantoin substantially.

The acid buflered N-chlorohydantoin compositions have a stability in the solid state which compares favorably with widely used compositions hitherto employed such as the powder composed of N,N-dichloroazodicarbonamidine, alkaline buffer and wetting agent in the proportions disclosed in U. S. Patent 2,263,948. This latter was stored in a closed chipboard container at 90 F. and relative humidity for 28 days. Another drypowder composed of 12.6 parts of micronized 1,3-

dichloro-5,5dimethylhydantoin; 79 parts of pul-- verized sodium dihydrogen phosphate monohydrate and 8.4 parts of sodium dodecylsulfate was also stored under the same conditions. At the end of this period the acid buffered chlorohydam toin composition had lost only 4% of its active chlorine, Whereas the alkaline buffered N,N-dichloroazodicarbonamidine composition had lost l3% of its active chlorine.

Compositions of this invention are particularly useful for rinsing cooking and eating utensils to kill bacteria which may be present on their surfaces.

The above description and examples are intended to be illustrative only and no unnecessary limitations should be understood therefrom.

What is claimed is:

An aqueous germicidal rinse composition comprising, approximately, one part of 1,,3-dichloro- 5,5-dimethylhydantoin, one part of 5,5-dimethylhydantoin, two parts of sodium dodecyl sulfate and. ten parts of sodium dihydrogen phosphate. FRANKLIN T..PETERS.

REFERENCES CITED The following references are of record, in the file of this patent:

OTHER REFERENCES Bittenbender et al., Ind. 8: Eng. Chem, vol. 31, No. 6, 1939 pages 742-744.

Food Industries, October 1940, pages 99-100- 

